Researchers recover human environmental genome without skeletal remains

Humans inhabited the cave of Satsurblia in various periods of the Paleolithic age. So far, researchers have sequenced only a single human individual from that site, dated from 15,000 years ago. In the older layers of the cave, no other human remains could be found.

Overview of the excavation works of Satsurblia cave in 2017. Image Credit: © Anna Belfer-Cohen.

The novel technique, employed by an international team of researchers headed by Prof. Ron Pinhasi and Pere Gelabert with Susanna Sawyer of the University of Vienna together with Pontus Skoglund and Anders Bergström of the Francis Crick Institute in London, enables the identification of DNA in environmental material samples. This was achieved through huge data analysis resources and extensive sequencing.

This approach has enabled an environmental human genome to be recovered from the BIII layer of the cave. This genome is dated nearly 25,000 years ago, before the Ice Age.

The new technique has demonstrated the viability of recovering human-environmental genomes even if skeletal remains are absent. An investigation of the genetic material has shown that the SAT29 human-environmental genome symbolizes an extinct human lineage that led to the existing West-Eurasian populations.

The researchers validated their findings by comparing the recovered genome with the genetic sequences acquired from bone remains of the adjacent cave of Dzudzuana, which returned conclusive evidence of genetic similarities. This fact verifies the results and rules out the possibility of modern contamination of the samples.

Apart from the identified human genome, other genomes like bison and wolf have been recovered from the environmental samples. The researchers used the sequences to rebuild the bison and wolf Caucasian population history, which will help gain better insights into the population dynamics of these species.

Currently, the researchers plan to carry out further investigations of soil samples from the Satsurbia cave with the aim of unraveling interactions between extinct fauna and humans and the impact of climatic changes on mammalian populations. The potential to recover DNA from soil samples enables reconstructing the evolution of entire past ecosystems.